An inkjet printing system typically includes one or more printheads and their corresponding ink supplies. Each printhead includes an ink inlet that is connected to its ink supply and an array of drop ejectors, each ejector consisting of an ink pressurization chamber, an ejecting actuator and a nozzle through which droplets of ink are ejected. The ejecting actuator may be one of various types, including a heater that vaporizes some of the ink in the pressurization chamber in order to propel a droplet out of the orifice, or a piezoelectric device which changes the wall geometry of the chamber in order to generate a pressure wave that ejects a droplet. The droplets are typically directed toward paper or other recording medium in order to produce an image according to image data that is converted into electronic firing pulses for the drop ejectors as the recording medium is moved relative to the printhead.
A common type of printer architecture is the carriage printer, where the printhead nozzle array is somewhat smaller than the extent of the region of interest for printing on the recording medium and the printhead is mounted on a carriage. In a carriage printer, the recording medium is advanced a given distance along a media advance direction and then stopped. While the recording medium is stopped, the printhead carriage is moved in a direction that is substantially perpendicular to the media advance direction as the drops are ejected from the nozzles. After the carriage has printed a swath of the image while traversing the recording medium, the recording medium is advanced; the carriage direction of motion is reversed, and the image is formed swath by swath.
The ink supply on a carriage printer can be mounted on the carriage or off the carriage. For the case of ink supplies being mounted on the carriage, the ink tank can be permanently integrated with the printhead as a print cartridge so that the printhead needs to be replaced when the ink is depleted, or the ink tank can be detachably mounted to the printhead so that only the ink tank itself needs to be replaced when the ink is depleted. Carriage mounted ink tanks typically contain only enough ink for up to about several hundred prints. This is because the total mass of the carriage needs be limited so that accelerations of the carriage at each end of the travel do not result in large forces that can shake the printer back and forth. As a result, users of carriage printers need to replace carriage-mounted ink tanks periodically depending on their printing usage, typically several times per year. Consequently, the task of replacing a detachably mounted ink tank should be simple and reliable within the printer.
The printhead nozzle array is fabricated, for example, on a silicon wafer that is then separated into many printhead die. The printhead die includes not only one or more nozzle arrays, but also electrical interconnect pads to receive signals from the printer controller, and fluid inlets to receive ink from corresponding ink supplies in the printer. In order to keep the fabrication costs of the printhead die low, the feature size on the printhead die is small so that the die size can be small and many die can be made on a single wafer. As a result, microelectronic and microfluidic packaging of the printhead die are required in order to facilitate a user installing it in the printer in such a way that electronic connections and fluidic connections are reliably made, with the nozzle arrays suitably aligned to provide excellent image quality. Typically one or more printhead die are adhered to a die mount substrate that includes fluid passageways corresponding to the fluid inlets on the printhead die. A separate electrical interconnect member, such as a flex circuit that includes bond pads for interconnection with the printhead die and an array of contact pads for connection to the printer, is also attached with the bond pads near the printhead die. The die mount substrate is then mounted to a printhead frame using screws, heat staking or other such fasteners.
U.S. Pat. No. 5,652,610 discloses a printhead die 1300 mounted on a substrate 1310 that is attached to an ink 1000 using a snap-fit and hinged closure 1200 (see FIG. 3). Although it is indicated in column 4 of U.S. Pat. No. 5,652,610 that the ink tank and the ink head may be separable from one another, it appears that this would be unwieldy for the user to do in a printer because the substrate 1310 is sandwiched between the ink tank 1000 and the closure 1200.
Inkjet ink includes a variety of volatile and nonvolatile components including pigments or dyes, humectants, image durability enhancers, and carriers or solvents. A key consideration in ink formulation and ink delivery is the ability to produce high quality images on the print medium. Image quality can be degraded if air bubbles block the small ink passageways from the ink supply to the array of drop ejectors. Such air bubbles can cause ejected drops to be misdirected from their intended flight paths, or to have a smaller drop volume than intended, or to fail to eject. Air bubbles can arise from a variety of sources. Air that enters the ink supply through a non-airtight enclosure can be dissolved in the ink and subsequently be exsolved (i.e. come out of solution) from the ink in the printhead at an elevated operating temperature, for example. Air can also be ingested through the printhead nozzles. For a printhead having replaceable ink supplies, such as ink tanks, air can also enter the printhead when an ink tank is changed.
Commonly assigned U.S. patent application Ser. No. 12/614,487 discloses removal of air from the ink in a printhead, as well as ink chamber and die mount substrate geometries that can facilitate air bubble removal. The disclosed ink chamber and die mount substrate geometries provide a more vertical pathway in the printhead for air bubble flow from the printhead die and from the ink inlet ports to an air space above the liquid ink level in the ink chambers from which the air can then be extracted. In particular, the ink chambers have a staggered outlet port configuration, and the die mount substrate includes ink pathways having a staggered ink inlet configuration to receive ink from outlet ports of the ink chambers.
What is needed is a compact die mount substrate that facilitates low-cost easy assembly onto a printhead frame, and particularly for a printhead frame that allows replacement of detachable ink tanks within an inkjet printer. In addition in some embodiments, the die mount substrate should be compatible with a staggered ink inlet configuration at the ink receiving surface of the die mount substrate.